Sniper stalling & restarting.

[Zapotjo]

I have a 1968 Corvette, with a 350 engine with about 435 HP. I have in the past had issues with noise in the systen so I completely rewired the system with three dedicated main 12 volt feeds for the Sniper, the Dual Sync distributor and the MSD box. I also added separate main feeds for the ignition side through relays. I also added 8 AWG ground feed directly from the battery to the engine block. I also redid all of the body groung points and cleaned any other ground points. After this I purchased a new Sniper Stealth. I still had some issues and thought I found the problem in a battery disconnect. I removed the disconnect and the engine was happy for three months it ran perfect. About a month ago, I started to recover the seats and replaced a bad interior light switch. This morning after the car sat for about a month, while working on the seats I took it out for a drive and the problem of shutting off, stalling and backfiring started again. I've attached a Config File and a datalog. I'd appriciate any input before I start trying find the issus because, I'm at a loss as to where to even start troubleshooting. I looks to me like the RPM just bottom out then suddenly comes back not to gracefully. It does not look like there's any data drop or at least I cant see it.
Really could use some help with this It got so bad by the time I got home, I can't even keep the engine running for longer than 10 or 15 seconds. Thanks in advance for any help with this. Joe

[GPatrick]

The file with the .INFO extension is not the Config File. The file you need to upload has a .SNIPER extension.

The immediate problem is pretty apparent. You're experiencing a complete loss of your RPM signal. At about 85 seconds into the datalog, there are many events but there are multiple areas were RPM has dropped to or nearly to zero. Since you have a Dual Sync distributor, check the wiring carefully at any connection between the distributor and the Sniper. You may have installed an adapter pigtail for the Dual Sync distributor, check those connections as well. Look for loose pins or poorly crimped wire to pin connections. Some of the older Dual Sync distributors had issues with corrosion internally. Remove your distributor cap and inspect around the sensor. The RPM dropout does not look like EMI/RFI.

If you're not sure what to look at, open the datalog and plot only RPM initially. Notice that RPM is tracking along and then at 58.95 seconds it drops to nearly zero. However, there's an "event" that takes place over about .2 seconds. Either a connection is opening up or the distributor is failing to transmit an RPM signal. Please post your Config File and we can see if there are any tune related items that might tend to lead to higher changes for internal corrosion. Incorrect synchronization of the distributor or an incorrect Inductive Delay can lead to internal arcing, for example.

[Danny Cabral]

Since RPM is derived from the crank sensor, start by troubleshooting the distributor's Hall-Effect sensor or its wiring. If it's a 1st generation Holley EFI Dual Sync distributor (LINK), you may end up replacing it.

Originally Posted by Danny Cabral The Sniper/Terminator X doesn't record System Logs because it's only capable of external datalogging (PC software or 3.5" TSLCD). If a regular datalog indicates an "RPM Error" when scrolling through the problem area, then troubleshoot why the crank or cam sync unit isn't transmitting a signal. Troubleshoot the crank & cam sensors, wiring, reference voltage & ground, reluctor, alignment, air gap (LINK), radial run-out problems (LINK), etc. Troubleshooting 3-wire Hall-Effect sensors: https://www.yumpu.com/en/document/read/ (Understanding/Troubleshooting Hall-Effect Sensors - "Troubleshooting", Page 2) https://www.team-bhp.com/forum/attac...e-beatbook.pdf (Fluke Multimeter Testing - "Hall-Effect Sensors", Page 17)

[Zapotjo]

I agree there's no EMI/RFI, I beat that issue to death. I also agree with your assessment of the RPM signal. I've always thought that the distributor was the issue, but in past post I there was a small amounts of EMI/RFI, so that's was what the Holley tech thoughts was the problem. Now here's where I'm getting frustrated with Holley as this the second unit I have purchased. However, Holley did agree to swap the original Sniper for a carb. So oddly enough I purchased a new Sniper Stealth because I liked how well it worked, when it works. I also purchased a new harness and replaced the old one. I also cleaned out the distributor since I noticed it was rusty looking inside. So is there a way to prevent this from happening? What's odd the car is not driven in the rain and stored inside. I thought it was condensation. To add insult to injury, I smelled gas when I was checking for loose wires today so the wires are not the problem (I think anyway). I also noticed the new fuel regulator was leaking due a cracked housing around the test port plug. This regulator was purchased when the new Sniper Stealth was purchased since the Stealth requires a different regulator. For something that works so well at times it's a shame there's not better quality control. I've attached what I hope is the correct file. And thank you very much for your time, I really do appreciate it.

[GPatrick]

I'm not sure what the cure is for the internal corrosion but the issue has come up more than a few times. Check the mounting of the sensor carefully. To me, it seems more electrical than mechanical internal to the distributor. When it is working right it is providing a clean signal. I can see that you have made adjustments to the Inductive Delay and assume that you resynchronized the distributor when installed in this engine.

There have been issues with the distributor harness connector pins and that could cause intermittent problems. Is any of the distributor to Sniper wiring running near plug wires or the alternator wiring? It is not RFI that is causing ECU resets, but it could cause noise in the RPM signal. I would just expect it to be more constant and erratic, but it should be considered.

Two things you can look at once you get the RPM signal sorted out. First, the Base Timing Table is a typical Sniper created mess. The Base Timing Table is especially bad in the low RPM low vacuum region. This article shows/explains the issue: https://www.efisystempro.com/efi-pro...timing-control. Your Base Timing Table looks similar to the one illustrated about 1/3 of the way down the page. If you would like assistance in creating a better baseline Base Timing Table let us know.

The other item is your Target AFR numbers. The engine wants what it wants, but it appears to be setup a little rich in the idle and WOT areas. You may have done testing, but if not, it may run a little better with an idle Target AFR closer to 13.8-14 instead of 13.5. And your WOT value of 12.3 is a little rich and the engine may respond better to a Target AFR closer to 12.8 or 12.9. Check your plugs and if it seems to be running OK you may want to just leave the targets alone. But if they look likes it's burning a little rich, you have some room to safely set it up a little leaner.

[Danny Cabral]

https://forums.holley.com/showthread...483#post261483 (Base Timing Table Generator - Excel Spreadsheet)

[Zapotjo]

Thanks Patrick and Danny. I'll check the wiring again. I've moved all of the wiring away from the plug wires, as well as any of the Sniper's other wires. The Inductive Delay was adjusted and the Dual Sync distributor was synchronized several times, but I'll check again. What I don't get is how it could run perfectly for four or five months, several thousand miles, then letting it sit for a month while working on the interior could have it go off the deal end like this? As far as the AFR and Timing I've had it all over the place and this is just the latest version. So I'll check out the article and adjust the AFR, but I could also use some help with both the timing and fuel tables. I know just enough to be dangerous as the saying goes. I fear the problem with the RPM loss is in the distributor. So my plan is to do nothing other than cleanup the Dual Sync distributor and test drive it, then check the connectors and test drive it. I want to find out what's causing the issue. The last time it happened I did too many thing at once and didn't know exactly what fixed it.

[Zapotjo]

Hi Patrick and Danny.
I've just completed the distributor and wiring check.I did not find any loose or broken connectors, I also had the adapter connectors and the Dual Sync distributor connectors tied together, so I don't think there was any issue with the wiring routing or the connectors.
Upon inspection of the distributor I found a light coating of rust, but the cap & rotor seemed fine. There's about 3K to 4K on the engine since being built and the Sniper being added.

What I did find: One of the Four screws that hold the circuit board to the distributor housing had backed out two were tight including the one at the crank sensor the other was loose, but not backed out. I tightened the one that was loose, but the other one seems to be striped out, so it looks like I need a need distributor.
Any thoughts on this? I don't want to buy another distributor if I don't have to, anything else I can check?
Also, if I have to buy another distributor will the HyperSpark work with the existing MSD 6AL CDI box? Looks to be cheaper price-wise. I only have the Dual Sync becaues that's what was with the complete kit originally. I don't think I need it from what I've read.

[GPatrick]

For the Sniper you only need the HyperSpark. When looking you may find that they have two versions based on the distributor gear - steel or iron. Make sure you select the one that is correct for your camshaft. The HyperSpark normally plugs directly into the Sniper harness without an adapter. If you wired your Dual Sync directly, you may need to re-wire a bit.

I'm not aware of any other testing that can be done on the distributor. Can you epoxy the part where the screw is stripped for the sake of testing to see if the RPM signal clears up?

If you do swap to the HyperSpark you'll have to change the ignition type using the handheld and alter the Inductive Delay and Reference Angle to match the HyperSpark.

EFI System Pro, for example, sells Holley equipment for the same price as any of the big box stores and they can direct you to the correct part number for your setup.

[Zapotjo]

Thank GPatrick. I really don't trust the Dual Sync distributor anymore, it looks like the HyperSpark should be more dependable. You guys are great with your replies and knowledge. Thanks, Joe.